1. Field of the Invention
The invention relates to tube coupling devices.
2. Background Prior Art
UK Patent Specification No. 1520742 discloses a coupling body having an internal throughway open at one end to receive a tube with a locking device in the open end of the throughway to lock the tube in the coupling body. UK Patent No. 2172948 discloses a development of that arrangement in which an insert sleeve is mounted in the open end of the throughway in which the tube locking device engages. The sleeve is held in the throughway by means of a spring ring embedded in the sleeve and having an obliquely inclined outer periphery which bears against and grips the surface of the throughway. Because the spring ring is almost entirely embedded in the insert sleeve, its freedom to flex and therefore its ability to cater for any significant tolerance in the diameter of the throughway is restricted.
These problems were addressed in European Patent No. 0373272 in which the coupling body was designed to be mounted in a bore in a housing rather than serve as a free-standing element. The coupling body has an encircling groove and a detent ring with an angled outer periphery is moulded into one side of the groove with the angled outer periphery of the ring extending across the groove and therefore be free to flex to cater for variation of the diameter of the socket. This arrangement provided a secure mounting for a coupling body in a housing but the coupling body is difficult to mould because of the angled outer periphery of the spring ring which makes it difficult to extract tooling for forming the groove. In a further development, the subject of European Patent No. 0751334, a coupling body is formed in two parts, one component having a bore in which the other component is mounted, the latter component having a spring metal ring with outwardly projecting fingers mounted in one side of a groove so that the fingers are bent over as the inner body is inserted into the outer body to retain the inner body in engagement in the outer body. In order to enable the outer ends of the fingers of the rings to be bent over as the inner body is inserted in the outer body, the metal ring has to be made fairly flexible and so the arrangement is more suitable to more lightly loaded components.
European Patent No. 0819880 discloses a tube coupling body of circular external cross-section having an internal throughway open at one end to receive a tube with a locking device in the open end of the throughway to lock a tube in the coupling body, the coupling body having on its outer side an encircling groove spaced from said one end of the body and a grab ring mounted in the groove of V-shaped cross-section facing the axial direction of the ring towards said one end of the coupling body, one limb of the V being lodged in the groove and the other limb projecting from the groove at its free end for gripping engagement in a bore in which the coupling body is inserted.
The grab ring provides a high strength griping device for locking the coupling body in the bore or socket in another component. As such, the arrangement is particularly suitable for use in combination with the high strength collet arrangement described and illustrated in European Patent No. 0764808. The arrangement is however also suitable for use with a wide range of different coupling body mountings.